The invention relates generally to the determination of the orientation of an exposed length of photosensitive material, e.g., photographic film.
More particularly, the invention relates to the determination of the orientation of an exposed length of photosensitive material having a timing track on one of its longitudinal margins The timing track includes a begin mark, a finish mark different from the begin mark, and a regular light/dark grating, i.e., a grating consisting of alternating light and dark bars of uniform width, between the marks.
Determination of the orientation of exposed photographic film is important in a printer or copier. To obtain properly oriented paper prints of exposed photographic film, it is necessary for the emulsion side of the film to be correctly positioned in the optical path of the printer. This can be accomplished by reading letters or numbers which are imaged on a margin of the film. However, this procedure can present problems, particularly in so-called mini-labs, because mini-labs are normally designed such that the entire printing process from insertion of the film to delivery of the paper prints is fully automated thereby allowing personnel with relatively little training to be employed. Accordingly, a method for automatically determining the orientation of an inserted film is desired.
The German Offenlegungsschrift 36 35 386 discloses a method in which a light beam is directed onto either side of a film and the relative amount of scattered light and reflected light is measured. It is assumed here that the emulsion side has a higher proportion of scattered light. However, this method could not be applied up to the present due to a lack of precision.